That's a man's work!... (no offence if you are a woman)
Perfect, now all you need is a gate-T so you can manually route heat into the house in the winter!
Don't forget to varnish that wood! (Or wax it)
You may want another intake, if that doesn't have a booster-fan in there too. Always have a larger intake than exhaust, because the exhaust is compressed and the intake is negative. You want to reduce negative pressure so it does not pull air from other doorways or windows or wall-outlets.
I'm not going to bother to varnish. I may paint it white to further seal. I plan to take it out in a few months after summer. I assume GPU mining won't be profitable by next summer. If the furnace was nearby I would vent it through the house but its not.
Those fans arn't really made to do that job, though depending on your container size, a few of them WILL get it done nicely. Just 1 is testing it IMO. What you really want is a centrifugal fan; 300+CFM, and made to overcome static pressure; loud and overkill mostly. The most well respect brand for quietness is Can-Fan.
But only 8GPUs you should be fine without that. Keep your gpu box as small as you can, another duct booster and you should be fine.
I had seen some pics of setups but didn't know a brand for those high power fans. I'm going to test the temps before enclosing and then will add more of those cheap 6" duct fans if necessary to get things to work.
I didn't finish my 8 card case so I'll get it done in a day or so. Some family things took priority.